(1) Field of the Invention
The present invention relates to a pointer illuminator, more particularly, to pointer illuminator including: an optically transparent pointer member having a reflecting surface for a pointer, which surface reflects light incident on a predetermined surface of incidence and guides the light to a tip (i.e. front end) of the pointer; a light source arranged around a drive shaft of the pointer member; and an optically transparent light-guiding member which guides light from the light source to the surface of incidence of the pointer member.
(2) Description of the Related Art
Currently, a pointer of a meter for a motor vehicle has an illuminating function to ensure good visibility when a meter having an illuminating function at night or a selfluminous meter is being used in the nighttime and in the daytime. As shown in FIG. 16, light L from a light source 2 (valve, LED) placed on a meter board 1 is introduced into a pointer 3 from a light-receiving surface 4 on the side of the pointer 3 and is finally guided out from the pointer 3 by using a diffusing/reflecting layer 5 by means of a hot stamping or fine prism, so that the illumination is performed.
Moreover, an area of the light-receiving surface 4 on the side of the pointer 3 is forced to be small because of a requirement in designing (i.e. the pointer 3 being thin and bright as much as possible) and a weight limitation of the pointer 3 (i.e. weight limitation of a subject being driven by a motor for rotating the pointer). Accordingly, as shown in FIG. 17, a plurality of the light sources 2 are placed to realize a bright pointer illumination without brightness nonuniformity throughout the whole area where the pointer 3 is rotated. However, as illustrated with a diagonal lines in FIG. 17, in fact, an area of the light-receiving surface 4 of the pointer 3 is small, therefore only a part of the light L coming out from a plurality of the light sources 2 enters the pointer 3. That means a great deal of light loss.
In order to solve the above problem, i.e. the great deal of light loss, as shown in FIG. 18, Japanese Patent Application Laid-Open No. 2004-294344 proposes a method, in which light L from a plurality of light sources 2 is collected in the proximity of a shaft by using a first reflecting surface 7 located within a light-introducing member 6, then thus collected light L is allowed to pass a second reflecting surface 8 which causes the collected light L to be reflected toward a third reflecting surface 9 and then finally, the reflected light L reflected by the third reflecting surface 9 is allowed to enter the pointer 3.
Further, when the light L coming out from the light source 2 has a certain angle of outgoing, the light enters each reflecting surface 7, 8, 9 with various angles. Each reflecting surface 7, 8, 9 of the light-introducing member 6 is constructed with a simple inclination or curved surface, therefore only the light L entering on a condition satisfying total reflection can be reflected. Since the light L coming out from the light source 2 with a certain angle of outgoing is narrowed to an angle satisfying the total reflection condition as much as possible, therefore in Japanese Patent Application Laid-Open No. 2004-294344, a light-guiding member 10 is placed between the light source 2 and the light-introducing member 6 so as to narrow the light L.
However, when the light-guiding member 10 is formed in a simple cylindrical shape as shown in FIG. 19, although it is possible to narrow the angle of outgoing of the light source 2, the degree of parallelization of the outgoing light L is low. As a result, a light loss tends to easily occur at the reflecting surfaces 7, 8, 9 where the light not satisfying the total reflection condition comes to the outside. That is, a part of the light L reflected at the first reflecting surface 7, which part is to be guided to the second reflecting surface 8, a part of the light L reflected at the second reflecting surface 8, which part is to be guided to the third reflecting surface 9, and a part of the light L reflected at the third reflecting surface 9, which part is to be guided to the tip of the pointer 3 are decreased, causing a problem that the pointer 3 cannot be illuminated with high brightness.
Further, when there are the light sources 2 each having a lens for narrowing the angle of outgoing and the angle of outgoing is very much narrowed, a range where one light source 2 can cover is decreased. Therefore, in such a case, many light sources 2 are required in order to cover the whole rotation range of the pointer 3, causing cost up. It may be also considered to decrease the light loss by subjecting each reflecting surface 7, 8, 9 to a mirror processing so as to decrease the light loss. However, it also causes cost up.
Further, according to the idea disclosed in Japanese Patent Application Laid-Open No. 2004-294344, the third reflecting surface 9 is placed on a drive shaft 11 of the pointer 3 and actual illuminated region of the pointer 3 can be formed only on a region facing the tip of the pointer 3 from the third reflecting surface 9 situated on the drive shaft 11, whereas the illuminated region of the pointer 3 is required to be wide as much as possible for the purpose of good visibility and good design. Even the drive shaft 11 is desirably in the illuminated region. However, such a purpose is hardly realized with the construction disclosed in Japanese Patent Application Laid-Open No. 2004-294344, that is, good visibility or good design cannot be realized therewith.